Until the 1600s, the average annual rate of economic growth in human history was approximately zero, on a per capita basis. Economies developed haltingly and, by today's standards, minimally. Politics consisted of a long and bitter series of wars, revolutions, and coups, punctuating variously short or long periods of oppressive and corrupt rule. Regimes came and went, and borders were redrawn, and politics staggered from one empire, invader, or upheaval to the next. Doctors and scholars knew barely more than the ancients had known—in some respects, less. The word scientist did not exist; neither did the concept of science as we know it today.
Knowledge existed, of course, and impressive kingdoms appeared, and new technologies emerged. But an objective observer would probably not have said that the Europe of the late medieval period was better organized or more advanced than the Europe of the Roman Empire at its height. In the year 1500, alien visitors might reasonably have pegged Homo sapiens as a stuck species. "Come back in another 100,000 years," they might have concluded, "and maybe these goofballs will be interesting."
And then it all changed.
Three Liberal Orders
There were breakthroughs and advances before the Industrial Revolution, the American Revolution, and the scientific revolution. What was lacking was a social order capable of generating and then cumulating advances systematically. Systematic social orders require constitutions: systems of rules that channel human energies in pro-social directions.
All three of the great liberal social systems—economic, political, epistemic—are traceable to breakthroughs in the 17th and 18th centuries. All were pioneered by men who followed each other's writings and doings and who sometimes knew each other personally. They and their works were flawed with the inequities and blind spots of their eras (one of which is reflected in the fact that all of them were men). But the founders were not just blundering along; they self-consciously sought to create an alternative to the failed regimes of the past. The greatest of them were men of genius, whose acuity and sophistication remain astonishing even today.
The economic system has no formal constitution. It does have something like a founding document, in the form of Adam Smith's The Wealth of Nations, plus Smith's equally important and closely connected treatise on moral development and social behavior, The Theory of Moral Sentiments. Smith elaborated a sophisticated theory of where human cooperation comes from, how to encourage and exploit it, how to wire it into societies' rules and institutions. He argued that Thomas Hobbes was wrong to believe that the natural human condition is a war of all against all: Human beings are oriented toward cooperation as well as conflict.
People, Smith argued, come into the world equipped with what he called sympathy, or fellow-feeling; empathy is the word we might use today. We have a natural inclination to imagine how others see and feel, and to align our own perspectives and dispositions with theirs. Also, people come equipped with a desire to be trusted and respected by others. Through our desire for mutual esteem based on our empathetic intuitions, we can align our interests and form social bonds on a basis other than force or domination. True, human beings are also greedy and ambitious. Yet—here is Smith's most famous insight—a well-structured social order can harness those very traits to promote activity which benefits ourselves by benefiting others. If we get the rules right, millions of people of every imaginable skill and temperament and nationality can cooperate to build a fantastically complex device like a Prius or iPhone, all without the oversight or instruction of any central planner. If we get the rules right.
Smith's proposition seemed ridiculous, given that human history through his time was soaked in blood and oppression. His claim was redeemed only by the fact that it proved to be true. Although Smith did not invent markets, he notated the code which enabled a tribal primate, wired for personal relationships in small, usually related groups, to cooperate impersonally across unbounded networks of strangers, and to do so without any central authority organizing markets and issuing commands. Economic liberalism—market cooperation—is a species-transforming piece of social software, one which enables us to function far above our designed capacity.
Political liberalism grapples with another version of the cooperation problem: Can we make rules that channel self-interest, ambition, and bias to benefit society as a whole? Can we provide social stability without squelching social dynamism, and without submitting to a Hobbesian authority? Yet another version of the cooperation problem preoccupies epistemic liberalism: Can people with sharp differences of opinion be induced to cooperate in building knowledge, again providing both stability and dynamism without recourse to authoritarianism?
Solving those problems requires a constitution, in a broad sense of the word: not necessarily a piece of paper or a formal law, but a social operating system that seeks to elicit cooperation and resolve differences on the basis of rules, not personal authority or tribal affiliation or brute force. In that sense, the liberal economic, epistemic, and political systems all have constitutions, even if only the political constitution is written down. (Even then, the written U.S. Constitution is only words on paper. The real Constitution is a dense system of explicit and implicit social rules, many of which are not written down.)
All three liberal constitutions organize far-flung cooperation, distribute decision making across social networks, and exploit network intelligence (where the system knows much more than its constitutive individuals), all with a minimum of centralized authority or control. They all emphasize impersonal rules over personal authority, open-ended processes over fixed outcomes, and consent over coercion. They all take as their starting point that individuals are by nature free and equal, and that freedom and equality are important and valuable. They are all extraordinarily successful, especially compared with the alternatives.
Which is not to say they are perfect. Far from it. But they are much better than their competitors at adapting to change and at identifying mistakes and self-correcting. And they are much better at averting the destructive social conflict Hobbes believed was the only alternative to authoritarian government.
For exactly that reason, all three liberal social systems can seem disquieting and unnatural. They allow for no ending points, no final arrival, no absolute certainty, no shelter from change. They place strains on local relationships and tribal ties. They can be harsh and unfair. They are difficult to understand and explain; indeed, they are deeply counterintuitive. They all depend on complex, intricately balanced rules, norms, institutions, and moral values, most of which did not arise organically but took centuries to construct. Acculturating people to all those rules and norms and institutions and moral values requires years of socialization and deep reservoirs of civic mutuality and trust. As a wag said: Where establishing the rule of law is concerned, the first five centuries are the hardest.
The story of the founding of the American political order needs no retelling here. We all know its characters, documents, and dates. By contrast, the epistemic revolution had no constitutional convention, no founding document, no date we commemorate. It emerged gradually, bit by bit. But there were founders, and foundations.
Locke's Political Revolution
The wars of religion wracked Europe not just for years but for generations. They spanned the whole continent, plus England. They brought a mass uprising in central Europe, a revolution in England, civil wars in France, and clashes of what were then the world's mightiest armies. European wars mowed down not only combatants but large numbers of civilians. "These more-than-religious wars were destructive, expensive, and inconclusive," the historian Brad S. Gregory writes. "By the middle of the seventeenth century they had drained and exhausted Europeans." The wars left traumas and scars whose effects linger to this day.
Many wars are long and scarring, but the religious wars were supposed to be about something. The contests between Catholics and Protestants, and also among Protestants (whose internecine disagreements rivaled their disagreements with Catholics), were about power and political advantage, as all wars are. But they also were about theology, priestly authority, biblical interpretation, ritual.
Notice, in that context, the last word of Gregory's formulation: "These more-than-religious wars were destructive, expensive, and inconclusive." Politically, the wars ended in the mid-1600s with the Peace of Westphalia, which amounted to a nonaggression pact in which sovereigns agreed not to interfere in each other's internal affairs and to tolerate minority religions. Epistemically, the outcome was similarly stalemated. "By the 1650s, theological experts [had] come no closer to reconciling their disagreements than they were in the 1520s," Gregory writes. "Conflicting claims about Christian truth were no more settled by 1648 than they had been in the 1520s."
Also unanswered was an even more important question: Who should settle disagreements—religious, political, epistemic? Does authority over truth reside with the Catholic Church, with the Protestant laity, with heads of state, or elsewhere? In religious controversies, who is the boss? That was the question that triggered and defined the wars. Yet violence had failed to resolve it. The conflicts had proved the costly futility of relying on contending authorities and force of arms to resolve differences of opinion. "Weary Europeans started looking for alternatives," Gregory writes.
Among those seeking alternatives was an English thinker named John Locke. Trained in medicine, he dabbled in politics and, for his trouble, found himself exiled to the Netherlands for five years, where he was steeped in the ideas of freethinkers like Baruch Spinoza and Pierre Bayle. Many thinkers and practitioners contributed to building modern liberalism, but if the source code were to be traced to just one man, he would have to be Locke. He stands unique among all the great thinkers in one respect: He was the germinal figure in the development of two branches of liberalism, political and epistemic.
In his politics, Locke was not a modern democrat. (In his day, no one was.) He accepted the authority of the British crown, and his advocacy of toleration drew the line at Catholicism and atheism. But he formulated three ideas that are foundational to political liberalism.
The first is the idea of natural rights: fundamental rules that apply to all persons from birth to death—rules that all other persons and also sovereigns and governments are bound to respect, and which are to be respected impersonally and reciprocally. Because they are natural, these rights inhere in human nature and are present in the state of nature. They provide a built-in limiting principle to the war of all against all. For Locke, the fundamental rights are life, liberty, and property (meaning not just material property but authority over one's own body and conscience). Because rights are inborn rather than earned by merit or conferred by social position, they inhere equally. Individuals are always equal in their fundamental rights, even as they differ in countless other ways.
A second foundational principle is rule by consent. Governments are not instituted by divine authority to rule the people; they are instituted by the people to enforce natural rights. If governments exceed their authority or use it to violate the people's rights, Locke argued, they lose their claim to govern and may rightly be replaced. Government is sovereign within its grant of power, but the ultimate sovereignty belongs to the governed.
Third, toleration. Religious differences had torn Europe apart, in good measure because the combatants assumed that if one religion is true, then others must be false. Because false religions endanger souls and deceive societies, they seemed intolerable. Religious war had shown how costly intolerance could be in practice, but even so, few thinkers questioned the principle that false belief was dangerous and should be stamped out. Hobbes, for example, believed that the state's stability depended on uniformity of religious belief, or at least uniformity of religious expression. Locke, by contrast, argued that force cannot save souls because it cannot change hearts—and even if it could, governments cannot be relied upon to discern religious truth. In any case, the person who worships wrongly does not injure others, and the state's business is not to save souls but to protect rights.
All of those ideas had precedents and echoes in other thinkers. Hobbes affirmed inalienable rights; the Levelers (an English reform movement of the 1640s) had called for popular sovereignty; John Milton and Roger Williams had argued for toleration. In Locke, however, we find pretty much the entire code, embedded for the first time in a worked-out theory. Natural rights, popular sovereignty, and toleration together make up something larger than the sum of the parts. Impersonal rules, neutrally applied; limited government, accountable to the people; pluralism of belief, and government that protects rather than persecutes dissent. The elements of modern liberalism are all there, although elaborating and applying them would be the work of centuries.
If Locke had ended his inquiries there, he would have earned his place as a giant. But he was not finished.
Locke's Epistemic Revolution
Michel de Montaigne was a politician and lawyer who had become exhausted by the conflicts of politics and sophistries of law. In the late 1500s, he shut himself in the tower of his family château, where he wrote essays that poked and prodded at received wisdom of all sorts, including the proposition that human beings could ever reliably know anything.
The wars of the Reformation and the Counter-Reformation made Montaigne profoundly pessimistic that any truth could be confidently asserted or any disagreement effectively resolved. In the longest and most influential of his essays, Apology for Raymond Sebond, he wrote that our judgment often leads us astray: "The slightest things in the world whirl it around." Our senses, he continued, convey only impressions of things, variably and unreliably; for all we know, we might be dreaming or hallucinating. "The uncertainty of our senses," he wrote, "makes everything they produce uncertain."
We may feel certain of truth, but such certainty is no guide. From his own experience of error, Montaigne knew that his own convictions were untrustworthy; by extension, the same must be true for everyone else's. Nor could we rely on reason—it is the servant of what today we call confirmation bias, an idea Montaigne impressively anticipated: "Everyone competes in plastering up and confirming this accepted belief, with all the power of their reason, which is a supple tool, pliable, and adaptable to any form." The world, he concluded, "is filled and soaked with twaddle and lies."
Montaigne also believed that we are doomed to eternal conflict over our beliefs: Because no two individuals see, hear, or believe the same thing, "we get into disputes at every turn." No wonder that "men are in agreement about nothing, I mean even the most gifted and ablest scholars, not even that the sky is over our head." The very fact that so many people disagree about so many things implies that all claims to knowledge are unfounded, for amid the cacophony, why should we assume that anyone is ever right about anything? "By this variety and instability of opinions," disputants "lead us as by the hand, tacitly, to this conclusion of their inconclusiveness."
Perhaps uncertainty and disputatiousness might be resolved by some all-knowing authority. But, demanded Montaigne, "Who shall be fit to judge these differences?" When the authorities themselves disagree, who will decide their disputes? Besides, no one is immune to error and misperception, and no one is dispassionate. "We would need someone exempt from all these qualities [of bias and passion], so that with an unprejudiced judgment he might judge of these propositions as of things indifferent to him; and by that score we would need a judge that never was."
Montaigne's demolition of knowledge appears, at first blush, to reflect almost nihilistic despair. Yet there are seeds here of something more. Notice, in his discussion, the emphasis on disagreement. The problem of truth, Montaigne hinted, is a social problem: a problem about reaching, or failing to reach, a working consensus. The knowledge problem centers not on what you know or what I know, but on what we know.
Two generations after Montaigne and two before Locke, the English philosopher Francis Bacon adopted some of Montaigne's skepticism but steered it in a different direction. Knowledge, he wrote in Novum Organum (1620), comes not from what truth seekers believe but what they do: make observations and perform experiments that eliminate wrong answers and point us toward right ones. Using this method, Bacon claimed, we can overcome the inherent flaws of our senses and cognition (what Bacon called "Idols of the Tribe"), the limits of our individual experiences and parochial viewpoints ("Idols of the Cave"), and the errors of received dogmas and superstitions ("Idols of the Theater").
"Bacon was a bad scientist," the sociologist of science Joseph Ben-David has argued, "and in many details he was not a very good philosopher either. There was little connection between the rise of new astronomy and mathematical physics and Baconian principles; experimentation without theory and collection of empirical knowledge had produced few scientific results." Bacon's importance lay in his method's implicit social promise. In an age of seemingly endless, fruitless creed wars, his experimental method suggested a conciliatory path: things people could do to reconcile their disagreements, taking their conflicts off the street and into the lab. "By sticking to empirically verified facts (preferably by controlled experiment)," Ben-David wrote, "the method enabled its practitioners to feel like members of the same 'community,' even in the absence of a commonly accepted theory. It was possible for scientists to go ahead with several competing views of the common subject matter and have the feeling of shared progress and eventual consensus. They no longer had to split into factions opposing each other on an increasingly wide and diffuse front, as the case had been before in philosophical conflicts."
Montaigne, Bacon, and the religious wars all were in the background when Locke published his Essay Concerning Human Understanding in 1689. Knowledge, he argued, is not innate; it is not something we are born with. Nor does it come from revelation, at least not when revelation is inconsistent with experience or existing knowledge. Nor can it come merely from general theories. Knowledge comes from experience and particulars (what today we might call facts and data), which we can find only by looking outside ourselves—by investigating the world and comparing notes with each other.
If our claims or hypotheses cannot be reduced to particulars and then checked against the experience and reason of ourselves and others, they are outside the boundaries of what today we call "science." Broad generalizations and abstract axioms, Locke said, are useful "in disputes, to stop the mouths of wranglers"—in other words, they make good debaters' points—"but [are] not of much use to the discovery of unknown truths, or to help the mind forwards in its search after knowledge."
Without checking our beliefs, we can have knowledge of our own existence and God's, Locke thought, but not much more. Moreover, without empiricism, we merely enshrine our mistakes. "All men are liable to error, and most men are in many points, by passion or interest, under temptation to it," he wrote. "Good men are men still liable to mistakes and are sometimes warmly engaged in errors, which they take for divine truths, shining in their minds with the clearest light."
What Locke was doing here was expelling from intellectual respectability—from the epistemic rulebook—claims which, because they are not checkable, are not adjudicable. Those claims, not incidentally, would include most of the theological and metaphysical disputes over which the wars of religion were ostensibly fought. Locke saw how untestable certitudes sparked irreconcilable social disputes. "The strength of our persuasions is no evidence at all of their own rectitude," he wrote, "and men may be as positive and peremptory in error as in truth."
When describing disputes that cannot be addressed empirically, Locke used the revealing word dangerous, at least when the disputes rise to the level of moral conflict: "Nothing can be so dangerous as principles thus taken up without questioning or examination; especially if they be such as concern morality, which influence men's lives, and give a bias to all their actions."
Locke's empiricism, then, is a social principle, and he understood it as such. It aims not just at knowledge but also at peace. Combined with his principle of toleration, it would have required the religious disputants of his day to seek paths toward resolving or dissolving their disputes; or else to change the subject and talk about something else—something they could resolve by finding facts and comparing experiences, rather than by coming to blows over divine revelation.
Notice how Locke's empiricism dovetails with the political principles of natural rights and basic equality. Because all people have eyes and ears and minds, and because we must check and consult with each other to find truth, the many, not just the few, are entitled to assert their own beliefs and contest others'. Epistemic rights, like political rights, belong to all of us; empiricism is the duty of all of us. No exceptions for priests, princes, or partisans.
This article is adapted from The Constitution of Knowledge: A Defense of Truth with permission from Brookings Institution Press, © 2021 by Jonathan Rauch.